Henry sqtjarebrigs mackay



Filed Nov. 20.

H S MACKAY PROCESS FOR TREATING GRES Nov. 27, 1923 Cil Patented Nov. 27, 1923.

UhllTEl) STATE.

HENRY SQUAREBRIGS MAOKAY, OF LONDON, ENGLAND.

PROCESS FOR TREATING GRES.

Application filed November 20, 1922.

To all 'ic/10m if 77mg/ concern.'

Be it known that l, HENRY SQUAnnBnnis Macu ii'. mining and metallurgical engineer, a subject ot the King ot Great Britain, residing at l- Broad Street Place, in the city ot' London, llngland, have invented certain new and useful liuprovcments in Processes t'or Treating Ores, of which the following is a specification.

This invention relates to a process for recovering scparatel;v and in successive stages the respective metals contained in complex ores such as sulphide ores contain` ing eine, copper, lead, silver and gold; whilev an important part of this process is applicable to the treatment ot lead or lead and silver ores for the recover)v ot' said metal or metals from said ores.

lily present invention provides (it) a process for extracting lead from ore or residues ot ore containing sulphates ot' lead which consists in leaching the ore with a chloride solution to extract the metals from the ore in solution and continuously precipitate the lead from the solution en iron in such a manner that the solution cannot be` come saturated with lead Jfrom the ore to such an extent that it will lose its etliciency as a solvent and a process for extracting lead and silver from sulphide ores or a mixture oliS sulphide aud oxidized orcs which consists in roasting the ore to convert the lead and silver sulphides ot the ore to lead and silver sulphates, leaching the roasted ore with a solution ot sodium chloride to torni chloride ot lead and silver in the solution` adding metallic iron to the solution to preeipiatetlie lead and silver l'roiu the solution and iorm a chloride olf iron in the :solution which can be used with or without so4 dium chloride as a solventlor the lead and silver sulphates iu the ore.

riel'lv stated. the present invention tor the treatment ot sulphide ores containing copper, zinc. lead. silver and gold is a chemical and electro-chemical process as follows:-

The ore is crushed in any suitable man` ner to about ti() mesh or other suitable mesh and roasted to convert the metal sulphides of the ere into a soluble form. The copper and Zinc are made soluble in a weak solution ot sulphuric acid and the lead and silver soluble in a solution of sodium chloride or ferrous chloride and the gold solublein a solution of potassium cyanide.

Serial No. 602,157.

The above and various other objects and advantages of this invention will be brought out in the following specification of the preferred manner of practicing the same, reference being made to the accompanying 'drawing which shows a flow sheet or a diagrammatic View of a plant suitable for practicing the process ot' this invention.

The ore is suitably crushed say to about (30 mesh, and is then roasted, for example in furnaces of MacDougal type or similar furnaces. The roasted calcines are next delivered into the central chamber of a lead lined Dorr thickener agitator A in which agitation with air takes place.

This standard Dorr thickener agitator A is constructed so that the agitation takes place in the central portion, and settling of the residues takes place in the outer portion. The residues settled are drawn out at the bottom and pumped to the top of the saine agitator er to another agitator thickener A2 following in the series as desired.

From the top of this lastna1ned agitator thickener A2 the clear solution flows to the agitator' A, and the residues are drawn from the bottom ot' A2 to a third thickener B. The clear solution is drawn from the top of thickener B to a lilter press C, such as of the Oliver type. The residues from filter C go to the lead section of the plant, and the clear Solution goes back to the thickener B and back from B to A2 and A.

A cold weak solution of sulphuric acid, :from an acid sto 'age tank or other suitable source. is added to agitators ."t and A as desired in sufficient quantity to dissolve all the soluble copper and zine in the calcines, and deliver a neutral solution from the top et' the thickeuer section olIv A to another agitator D.

ln agitzitiug the calciues in the sulphurie acid solution with air in agitator-s A and the iron is oxidized and :terric sulphate is formed; l `e2(S())3 as is also aluminium sulphate; A12 (S04) 3.

This neutral solution is passed into agitator D and zinc oxide is added and agitated with air.

The object of this is to form more zinc sulphate; ZnSOJ, so that when it is electrolyzed the acid that was combined as lle2(S(),) and l2(SU) will be recovered, and also to precipitate part of the other im` pui-ities from the Solution; such as bismuth, arsenic and antimony. The reaction which lit) takes placein Y a solution containing; Fe2 (S04) d-l2 (SQQ jfl-H2O when agitated in presence of zinc oxide is as 'tollows:-n Fe2 (SOQ fl-A12 (S04) 343112) -l-GZn) 1:

6Znso,+sre (o ifi) i-2in (on) 3 The ,iron and aluminium are precipitated as hydroxides.

The precipitates from agitator l), if they carry zinc oxide of commercial value, are returned to agitator A and the Zinc is recovered with the acid solution. It they do not carry sufficient value they are filter pressed and discarded the clear solution going into still another agitator E.

The clear solutions from agitator D are delivered into agitator lll Where iron dust is added to precipitate the iirincipal part of the copper, antimony, bismuth and arsenic.

The clear solution is delivered from agit'ator E to another agitator F, and theresi dues containing the copper are drawn lrom the bottom ot agitator E and delivered to another lter press L, of the @liver or other suitable type, where they are filter pressed. The filter press cakes go to a smelterM, or they may go hack to a roasting` furnace and be oxidized and dissolved in sulphuric acid and precipitated` by electrolysis.

Copper if present in sullicient quantity is precipitated by electrolysis to a point Where the solutions carry about 0.75% copper in the presenceoit` zinc sulphate, the balance ot copper is precipitated onl iron or zinc dust.

Thel copper precipitated can be either smelted or oxidized by roasting,y and re-dissolved in sulphuric acid and precipitated by electrolysis.

The extraction of the'zinc and copper may be effected substantially in the manner described in my United States patent specification dated Qlst April, 191e, No. LOM-,371.

TheV residues carrying` the lead are iirst agitated in hot sodium (,-hloride solutions in Dorr agitators and thickeners or other similar apparatus. l'letore the soli'itious become saturated with lead chloride the clear lead chloride solutions are continuously drawn ol'l' troni the ADorr tliii-lieners, and the lead precipitaltal vir. the lead may be pria-ipita'ted on' ironV (or any metal higher in the electrochemical series than lead) preteral'ily in the form of metal. dust-and the solutions regenerated and returned to the agitators.

This is a very important step in the process. Unless the lead is continuously precipitated from the solution, the saturation point is soon reached,and Vthe solvent action ceases. But in this process it is so arranged that the lead is'contin'uously' precipitated so that the saturation point is never reached. The solvent is continuously regenerated and never loses its eiciency;

The clear solution from the lilter press L goes to the agitator F. Zinc dust is added to the solution in. agitator F to precipitate the last traces of cadmium, iron, cobalt, nickel, antimony, bismuth, copper and 2113561110.

From the bottom oli agitator F the residues and solution are drawn into a Dori' thickener G, andthe clear solution drawn from the top of this thiclener Cf to a sand filter H, and the precipitates from the bottom oil the thickener G are-passed to another lilter press N, ot' the Oliver or other suitable type. The tilter cake is discarded and the clear solution from the filter press N is returned to the thickener (l.

The sand filter H frees the solution of all sediment and the purified solution passes into a storage tank l, from storture 'tank I the solution passes through the electrolytic cells J Where the zinc is precipitated and sul phuric acid regenerated; part ot the solution leaving the electrolytic cells .l passes back into the storage tank l to standardize the electrolyte, and part of it passes into another storage tank K, :from which the solution may pass back to agitator A to leach fresh ores.

Now as to the lead section of the plant,the lead residues from the aforesaid Oliver iil ter C pass into a Dorr agitator O Where they are agitated in a chloride solution. The solution and pulp are drawn from the bottom oli this agitator' O and pumped to the centre ot tliiclrener P.

After the lead residues are leached with sodium chloride in starting the process, and after the lead is precipitated, au iron fer; rous chloride is formed in the solution, and the leachinglr solutions then continue in the process containing,r sodium chloride and ferrous chloride. Ferrous chloride may be used as the leaching* solution wit-hout sodium chloride, but for economic reasons sodium chloride'should be used with Yferrous chloride.

lllhen the ore is roasted so that the lead is combined as Pbfl), the reactions-i which tatiey place are as Vliollowszm- Thus by precipitatinpr lead from its chlo ride with metallic iron au active solvent tor lead sulphate is termed as terroiiis chloride.

.fttt-er the lead is preciliiitated on iron, such as when the leaching` solution contains sodium chltiride, the 'Formulawill be as Vl'ollows:

Wl'lien this solution is used to leach the ore, both the ferrous chloride and sodium lll) fil

chloride ai'eavailable to forni chloride of lead as follows 1st reaction.

After the solutions are continuously used in leaching` the ore, and ferrous chloride increases in the solution to a point where it becomes a sufficiently active solvent for lead sulphate, then sodium chloride can be discontinued in the solution.

rllhe chemical reactions which take place in the solution without sodium chloride would be as follows Pbso,+r@oi,zrlboigreso, reci,afresoairezrbarreoigreso,

By this reaction ferrous chloride is regenerated and metallic lead precipitated.

lYhen this solution is continuously used in leachingl ore containing lead sulphate, ferrous sulphate increases in the solution. lVheii the ferrous sulphate reaches saturation point in the solution it can be crystallized out and saved as a by-product, or part of the solution may be discarded to prevent the ferrous sulphate from decreasing the efficiency' of the solvent. The chlorine lost by discarding a part of the ferrous chloride solution can be made up by adding sodium chloride to the solution.

The pulp is drawn from the bottoni of the thickener P and pumped to an agitator O. The clear solution is drawn from the top of this thickener P and flows to a sand filter R, and from the bottom of the sand filter R to a precipitating drum S where the lead and silver are precipitated on iron.

The solution from the bottom of the precipitating drinn S flows to a crystallizing tank f where it is cooled and where sodium, sulphate or ferrous sulphate is ciystallized out or returned direct. to agitator O.

rlhe solution is then drawn into a storage Vtank lV 'wherein it is standardized by add- 'ing sodium chloride, if required, and is then pumped back to agitator O to be used in the circuit to leach thc lead sulphate residues.

Then all the soluble lead is extracted from the residues, they are pumped to the tliickeners P and l" and thence to a lter press Q, and washed, the clear solution going back to the thickener l)2 and the filter cake going to the gold and silver recovery ilant.

The clear solution from thickeiiers and P2 to the sand filter R, precipitating drum S, crystallizing tank T storage tank lV, and back to the agitator O, or directly back to the agitator O. The lead precipis tates from drinn S are dra-wn off and washed in a revolving drum and thence go to the melting pot to be melted and refined by the ordinary wellknown methods.

The washed filter cake, discharged from the filter press Q of the lead section, is delivered into an agitator l and agitated With air in a solution of potassium cyanide.

The pulp from this agitator l is drawn ofi' from the bottom of this agitator and delivered to the centre of the Dori' thickener 2, and from the bottoni of this thiekener 2 back to agitator l. The pulp passes in this circuit until the soluble gold and silver are in solution. Their the pulp is passed into another thickener 3, where it is settled, and drawn from the bottoni of this thick ener 3 to an Oliver, or other suitable, filter press Ll, where it is filter pressed and washed and the filter cake discharged.

The clear solutions pass from the filter press 4 to thickener 3, and from the top of this thickener 3 to the centre of the thickener 2, and from the top of the latter to the clarifying filter 5, and from this last-named filter 5 to the precipitating boxes G.

Zine dust is added in the precipitating boxes G and the gold and silver are precipitated from solution.

The clear solution from the precipitatinor boxes G is delivered into the storage tank i where the solution is standardized with potassium cyanide and returned to agitator 1.

The gold and silver precipitates are delivered from the precipitating boxes G to the refining department 8 Where the gold and silver are separated and refined by the ordinary well-known methods.

The second part of this process may be employed for treating ores which carry silver in which case the ore is roasted in such a manner that practically all the lead and a large percentage of the silver is converted into the sulphates of these metals, l)bS(.)A,Ag2S0,. The silver so formed is recovered in solution as a chloride of silver, ZiigCl, and precipitated with the lead when metallic iron is added to thel solution as follows-using sodium chloride solution 2 Pbt( )ft-A gQSOl-l-JENaCl:

using` ferrous chloride solution the reactions are as follows riiso,i-Aasoereoi.:

Pb(I2tQr\gCl-}-QFeSO,-|2Fe:

Pb-tQAg-t-2l"eCl2-t2l4`eSO4x After thel lead and silver are precipitated, part of the solution is purified, as required,

by crystallizinp out the sodiuni sulphate or ferrous sulphate in accordance with the chloride solution used and the other part goes directly and continuously back to the leaching agitators. The part that is purified recovered vfrom the ore as aforesaid, the residues are tilter pressed and Washed, the solution Agoing to the lead precipitating section oli the plant and the residues to the Dorr agitators and thickeners ot the gold and silver section of the plant Where the reinainingresidues are leached with cyanidev potassium to recover the remaining gold and silver and precipitated on Zinc dust in the usual nianner adopted in the cyanideprocess.

In arrangingthe plant for this process the YDorr agitators of the lead leaching' sec-tion ot the plant can be enclosed in bricliworl( itt. desired leavingi a space between the brick- WorlaY and the outside of the steel leaddined agit-eters through which the hot ,gases troni the roasting` 'furnaces circulate to heat the sodium chloride leaching solutions.

T he lirst sectionl ofthe process Where the :eine and copper is extracted is or may be the saine as niy aforesaid known process for the extraction of copper and other metals.

The third section et the above process for the extraction of gold and silveris or may he the saine as the Well-known cyanide process.

The second section olx the above process rie: ttor the extraction oi the lead and silver new and what heretofore has been the link in a successful l-iydrol1netalprocess tor the separate extraction oi the 7aiions metals ll'roin co1'nple2\; orcs; and this second. section may he used sepa ra-la' 'for treating lead or letal and silver orcs i'or the recovery ot these nieta-ls troni their ores.

This missing' link connectiinr the Wellknown processes makes a new process and by the use of this combinationr process any complex Zinc, lead, copper, gold and silver ores can be successfully treated at much less cost than by any other process and niereorer this process avoids all snielting ot coinplex ore whether sulphides or otherwise.

This process makes vaina-blo deposits of comple); ore which heretofore have been of no Value.

What is claimed is zl. In a continuous process for extracting lead from ore Which consists in lirst conyerting the lead to lead sulphate next leachthe resulting Ore With a chloride solu* tion to extract the lead in solution from the ore, continuouslyT precipitatingthe lead troni the solution on a nietal such as iron in such a manner that the solution cannot be come saturate-d with the lead troni the ore io such an extent that it will lose its etliciency as a solvent, and continuously einployingg; the resulting solution to leach more ore containingv lead sulphate.

2. in a continuous process i'jor extracting lead 'troni ore which consists in lirst converting' the lead to lead sulphate, next leaching tha resulting ore with a. chloride solution to extract the lead in solution troni the ore, continuously precipitating the lead l'roin the solution so that the solution cannot become saturated with the lead from the ore to such an extent that it will lose its eiiciency a solvent, and continuously employing the reu sulting,- solution to leach inore ore containinpr lead sulphate.

3. In a continuous process for extracting loY l' and other metals troni ores which con si in roasting; the ore to convert the sulphides to sulphates` oitl the lead, leachinfb` the roastedY ore iifith sulphur-ic acid to torni sulphates oli the metal in solution, continuously precipitating the inetal troni the solution to recover reiined :metals and regenerating sulphuric acid to be used in the process and adding'v a chloride solution to the residues upon removal of the metals to torni chlorides ot' the lead and silver in solution, addinrcr iron to the solution to precipitate the lead and silver continuously 'troni the solution in such a manner that the solution cannot he saturatml with lead or silver lo such an extent as that it will lose ils eliiciency ag a solvent and continuously employing the resulting solution to leach nioro orc containing; lead sulphate.

ifilflNRY SQUARBRIGS lvlA CKAY. 

